| abstract |
A novel, pumpable, thermoplastic desiccated mastic capable of desiccating a sealed insulating glass unit. The compositions utilize adhesive materials which have a low vapor transmission rate but, nevertheless, have been found to effectively dry the air space in the unit. They do not contribute to chemical fogging and, in preferred embodiments, reduce or eliminate chemical fogging caused by other structures in the assembly. The compositions adhere well to the U-channel material and do not flow or sag under the normal range of service conditions encountered by an insulating glass assembly. The disclosed compositions comprise: 4-30 weight percent of a film former selected from the group consisting of polyisobutylene polymers having a molecular weight in the range of about 35,000 to about 60,000, and mixtures of such polymers with minor amounts of a butyl rubber having a molecular weight of up to about 500,000; 20-50 weight % of a non-crystalline homopolymer, copolymer, terpolymer or graft copolymer comprising polypropylene; 0-20 weight % of a low volatile UV stable tackifier compatible with the film former and polypropylene components; and 20-50 weight % of an adsorbent component comprising 20-50% by weight of the composition of a moisture or moisture and volatile organic chemical adsorbing material, and 0-10% by weight of the composition of an adsorbent of volatile organic compounds. |